in 2301, when we cover public opinion polls well discuss push polls. These are campaign ploys designed to expose respondents, who think they are talking to a real pollster, to negative information about a candidate. Since they ask questions on the order of: "Would you support John McCain if you knew he fathered a black child?" they do not slander people since they make no actual allegations, on what of statements. That was an actual push poll question by the way.
Now comes word that the technique continues to be used against Mitt Romney and John Edwards. Since they are not polls, but are in fact advocacy calls, some states mandate that this be made clear at the start of the call, but this is often not done.